A passive NNTP client that retrieves Usenet news articles from a remote server.

Submitted by:	James Raynard <fports@jraynard.demon.co.uk>

1 files changed, 1766 insertions, 0 deletions

diff --git a/news/slurp/files/dbz.c b/news/slurp/files/dbz.c
new file mode 100644
index 000000000000..b8b1886e7e0a
--- /dev/null
+++ b/news/slurp/files/dbz.c
@@ -0,0 +1,1766 @@
+/*
+
+dbz.c  V3.2
+
+Copyright 1988 Jon Zeeff (zeeff@b-tech.ann-arbor.mi.us)
+You can use this code in any manner, as long as you leave my name on it
+and don't hold me responsible for any problems with it.
+
+Hacked on by gdb@ninja.UUCP (David Butler); Sun Jun  5 00:27:08 CDT 1988
+
+Various improvments + INCORE by moraes@ai.toronto.edu (Mark Moraes)
+
+Major reworking by Henry Spencer as part of the C News project.
+
+These routines replace dbm as used by the usenet news software
+(it's not a full dbm replacement by any means).  It's fast and
+simple.  It contains no AT&T code.
+
+In general, dbz's files are 1/20 the size of dbm's.  Lookup performance
+is somewhat better, while file creation is spectacularly faster, especially
+if the incore facility is used.
+
+*/
+
+#include <stdio.h>
+#include <sys/types.h>
+#include <string.h>
+#include <ctype.h>
+#include <errno.h>
+#ifndef __STDC__
+extern int errno;
+#endif
+#include <dbz.h>
+
+/*
+ * #ifdef index.  "LIA" = "leave it alone unless you know what you're doing".
+ *
+ * FUNNYSEEKS	SEEK_SET is not 0, get it from <unistd.h>
+ * INDEX_SIZE	backward compatibility with old dbz; avoid using this
+ * NMEMORY	number of days of memory for use in sizing new table (LIA)
+ * INCORE	backward compatibility with old dbz; use dbzincore() instead
+ * DBZDEBUG	enable debugging
+ * DEFSIZE	default table size (not as critical as in old dbz)
+ * OLDBNEWS	default case mapping as in old B News; set NOBUFFER
+ * BNEWS	default case mapping as in current B News; set NOBUFFER
+ * DEFCASE	default case-map algorithm selector
+ * NOTAGS	fseek offsets are strange, do not do tagging (see below)
+ * NPAGBUF	size of .pag buffer, in longs (LIA)
+ * SHISTBUF	size of ASCII-file buffer, in bytes (LIA)
+ * MAXRUN	length of run which shifts to next table (see below) (LIA)
+ * OVERFLOW	long-int arithmetic overflow must be avoided, will trap
+ * NOBUFFER	do not buffer hash-table i/o, B News locking is defective
+ */
+
+#ifdef FUNNYSEEKS
+#include <unistd.h>
+#else
+#define	SEEK_SET	0
+#endif
+#ifdef OVERFLOW
+#include <limits.h>
+#endif
+
+static int dbzversion = 3;	/* for validating .dir file format */
+
+/*
+ * The dbz database exploits the fact that when news stores a <key,value>
+ * tuple, the `value' part is a seek offset into a text file, pointing to
+ * a copy of the `key' part.  This avoids the need to store a copy of
+ * the key in the dbz files.  However, the text file *must* exist and be
+ * consistent with the dbz files, or things will fail.
+ *
+ * The basic format of the database is a simple hash table containing the
+ * values.  A value is stored by indexing into the table using a hash value
+ * computed from the key; collisions are resolved by linear probing (just
+ * search forward for an empty slot, wrapping around to the beginning of
+ * the table if necessary).  Linear probing is a performance disaster when
+ * the table starts to get full, so a complication is introduced.  The
+ * database is actually one *or more* tables, stored sequentially in the
+ * .pag file, and the length of linear-probe sequences is limited.  The
+ * search (for an existing item or an empty slot) always starts in the
+ * first table, and whenever MAXRUN probes have been done in table N,
+ * probing continues in table N+1.  This behaves reasonably well even in
+ * cases of massive overflow.  There are some other small complications
+ * added, see comments below.
+ *
+ * The table size is fixed for any particular database, but is determined
+ * dynamically when a database is rebuilt.  The strategy is to try to pick
+ * the size so the first table will be no more than 2/3 full, that being
+ * slightly before the point where performance starts to degrade.  (It is
+ * desirable to be a bit conservative because the overflow strategy tends
+ * to produce files with holes in them, which is a nuisance.)
+ */
+
+/*
+ * The following is for backward compatibility.
+ */
+#ifdef INDEX_SIZE
+#define	DEFSIZE	INDEX_SIZE
+#endif
+
+/*
+ * ANSI C says an offset into a file is a long, not an off_t, for some
+ * reason.  This actually does simplify life a bit, but it's still nice
+ * to have a distinctive name for it.  Beware, this is just for readability,
+ * don't try to change this.
+ */
+#define	of_t	long
+#define	SOF	(sizeof(of_t))
+
+/*
+ * We assume that unused areas of a binary file are zeros, and that the
+ * bit pattern of `(of_t)0' is all zeros.  The alternative is rather
+ * painful file initialization.  Note that okayvalue(), if OVERFLOW is
+ * defined, knows what value of an offset would cause overflow.
+ */
+#define	VACANT		((of_t)0)
+#define	BIAS(o)		((o)+1)		/* make any valid of_t non-VACANT */
+#define	UNBIAS(o)	((o)-1)		/* reverse BIAS() effect */
+
+/*
+ * In a Unix implementation, or indeed any in which an of_t is a byte
+ * count, there are a bunch of high bits free in an of_t.  There is a
+ * use for them.  Checking a possible hit by looking it up in the base
+ * file is relatively expensive, and the cost can be dramatically reduced
+ * by using some of those high bits to tag the value with a few more bits
+ * of the key's hash.  This detects most false hits without the overhead of
+ * seek+read+strcmp.  We use the top bit to indicate whether the value is
+ * tagged or not, and don't tag a value which is using the tag bits itself.
+ * We're in trouble if the of_t representation wants to use the top bit.
+ * The actual bitmasks and offset come from the configuration stuff,
+ * which permits fiddling with them as necessary, and also suppressing
+ * them completely (by defining the masks to 0).  We build pre-shifted
+ * versions of the masks for efficiency.
+ */
+static of_t tagbits;		/* pre-shifted tag mask */
+static of_t taghere;		/* pre-shifted tag-enable bit */
+static of_t tagboth;		/* tagbits|taghere */
+#define	HASTAG(o)	((o)&taghere)
+#define	TAG(o)		((o)&tagbits)
+#define	NOTAG(o)	((o)&~tagboth)
+#define	CANTAG(o)	(((o)&tagboth) == 0)
+#define	MKTAG(v)	(((v)<<conf.tagshift)&tagbits)
+
+/*
+ * A new, from-scratch database, not built as a rebuild of an old one,
+ * needs to know table size, casemap algorithm, and tagging.  Normally
+ * the user supplies this info, but there have to be defaults.
+ */
+#ifndef DEFSIZE
+#define	DEFSIZE	120011		/* 300007 might be better */
+#endif
+#ifdef OLDBNEWS
+#define	DEFCASE	'0'		/* B2.10 -- no mapping */
+#define	NOBUFFER		/* B News locking is defective */
+#endif
+#ifdef BNEWS
+#define	DEFCASE	'='		/* B2.11 -- all mapped */
+#define	NOBUFFER		/* B News locking is defective */
+#endif
+#ifndef DEFCASE			/* C News compatibility is the default */
+#define	DEFCASE	'C'		/* C News -- RFC822 mapping */
+#endif
+#ifndef NOTAGS
+#define	TAGENB	0x80		/* tag enable is top bit, tag is next 7 */
+#define	TAGMASK	0x7f
+#define	TAGSHIFT	24
+#else
+#define	TAGENB	0		/* no tags */
+#define	TAGMASK	0
+#define	TAGSHIFT	0
+#endif
+
+/*
+ * We read configuration info from the .dir file into this structure,
+ * so we can avoid wired-in assumptions for an existing database.
+ *
+ * Among the info is a record of recent peak usages, so that a new table
+ * size can be chosen intelligently when rebuilding.  10 is a good
+ * number of usages to keep, since news displays marked fluctuations
+ * in volume on a 7-day cycle.
+ */
+struct dbzconfig {
+	int olddbz;		/* .dir file empty but .pag not? */
+	of_t tsize;		/* table size */
+#	ifndef NMEMORY
+#	define	NMEMORY	10	/* # days of use info to remember */
+#	endif
+#	define	NUSEDS	(1+NMEMORY)
+	of_t used[NUSEDS];	/* entries used today, yesterday, ... */
+	int valuesize;		/* size of table values, == SOF */
+	int bytemap[SOF];	/* byte-order map */
+	char casemap;		/* case-mapping algorithm (see cipoint()) */
+	char fieldsep;		/* field separator in base file, if any */
+	of_t tagenb;		/* unshifted tag-enable bit */
+	of_t tagmask;		/* unshifted tag mask */
+	int tagshift;		/* shift count for tagmask and tagenb */
+};
+static struct dbzconfig conf;
+static int getconf();
+static long getno();
+static int putconf();
+static void mybytemap();
+static of_t bytemap();
+
+/* 
+ * For a program that makes many, many references to the database, it
+ * is a large performance win to keep the table in core, if it will fit.
+ * Note that this does hurt robustness in the event of crashes, and
+ * dbmclose() *must* be called to flush the in-core database to disk.
+ * The code is prepared to deal with the possibility that there isn't
+ * enough memory.  There *is* an assumption that a size_t is big enough
+ * to hold the size (in bytes) of one table, so dbminit() tries to figure
+ * out whether this is possible first.
+ *
+ * The preferred way to ask for an in-core table is to do dbzincore(1)
+ * before dbminit().  The default is not to do it, although -DINCORE
+ * overrides this for backward compatibility with old dbz.
+ *
+ * We keep only the first table in core.  This greatly simplifies the
+ * code, and bounds memory demand.  Furthermore, doing this is a large
+ * performance win even in the event of massive overflow.
+ */
+#ifdef INCORE
+static int incore = 1;
+#else
+static int incore = 0;
+#endif
+
+/*
+ * Stdio buffer for .pag reads.  Buffering more than about 16 does not help
+ * significantly at the densities we try to maintain, and the much larger
+ * buffers that most stdios default to are much more expensive to fill.
+ * With small buffers, stdio is performance-competitive with raw read(),
+ * and it's much more portable.
+ */
+#ifndef NPAGBUF
+#define	NPAGBUF	16
+#endif
+#ifndef NOBUFFER
+#ifdef _IOFBF
+static of_t pagbuf[NPAGBUF];	/* only needed if !NOBUFFER && _IOFBF */
+#endif
+#endif
+
+/*
+ * Stdio buffer for base-file reads.  Message-IDs (all news ever needs to
+ * read) are essentially never longer than 64 bytes, and the typical stdio
+ * buffer is so much larger that it is much more expensive to fill.
+ */
+#ifndef SHISTBUF
+#define	SHISTBUF	64
+#endif
+#ifdef _IOFBF
+static char basebuf[SHISTBUF];		/* only needed if _IOFBF exists */
+#endif
+
+/*
+ * Data structure for recording info about searches.
+ */
+struct searcher {
+	of_t place;		/* current location in file */
+	int tabno;		/* which table we're in */
+	int run;		/* how long we'll stay in this table */
+#		ifndef MAXRUN
+#		define	MAXRUN	100
+#		endif
+	long hash;		/* the key's hash code (for optimization) */
+	of_t tag;		/* tag we are looking for */
+	int seen;		/* have we examined current location? */
+	int aborted;		/* has i/o error aborted search? */
+};
+static void start();
+#define	FRESH	((struct searcher *)NULL)
+static of_t search();
+#define	NOTFOUND	((of_t)-1)
+static int okayvalue();
+static int set();
+
+/*
+ * Arguably the searcher struct for a given routine ought to be local to
+ * it, but a fetch() is very often immediately followed by a store(), and
+ * in some circumstances it is a useful performance win to remember where
+ * the fetch() completed.  So we use a global struct and remember whether
+ * it is current.
+ */
+static struct searcher srch;
+static struct searcher *prevp;	/* &srch or FRESH */
+
+/* byte-ordering stuff */
+static int mybmap[SOF];			/* my byte order (see mybytemap()) */
+static int bytesame;			/* is database order same as mine? */
+#define	MAPIN(o)	((bytesame) ? (o) : bytemap((o), conf.bytemap, mybmap))
+#define	MAPOUT(o)	((bytesame) ? (o) : bytemap((o), mybmap, conf.bytemap))
+
+/*
+ * The double parentheses needed to make this work are ugly, but the
+ * alternative (under most compilers) is to pack around 2K of unused
+ * strings -- there's just no way to get rid of them.
+ */
+static int debug;			/* controlled by dbzdebug() */
+#ifdef DBZDEBUG
+#define DEBUG(args) if (debug) { (void) printf args ; }
+#else
+#define	DEBUG(args)	;
+#endif
+
+/* externals used */
+extern char *malloc();
+extern char *calloc();
+extern void free();		/* ANSI C; some old implementations say int */
+extern int atoi();
+extern long atol();
+
+/* misc. forwards */
+static long hash();
+static void crcinit();
+static char *cipoint();
+static char *mapcase();
+static int isprime();
+static FILE *latebase();
+
+/* file-naming stuff */
+static char dir[] = ".dir";
+static char pag[] = ".pag";
+static char *enstring();
+
+/* central data structures */
+static FILE *basef;		/* descriptor for base file */
+static char *basefname;		/* name for not-yet-opened base file */
+static FILE *dirf;		/* descriptor for .dir file */
+static int dirronly;		/* dirf open read-only? */
+static FILE *pagf = NULL;	/* descriptor for .pag file */
+static of_t pagpos;		/* posn in pagf; only search may set != -1 */
+static int pagronly;		/* pagf open read-only? */
+static of_t *corepag;		/* incore version of .pag file, if any */
+static FILE *bufpagf;		/* well-buffered pagf, for incore rewrite */
+static of_t *getcore();
+static int putcore();
+static int written;		/* has a store() been done? */
+
+/*
+ - dbzfresh - set up a new database, no historical info
+ */
+int				/* 0 success, -1 failure */
+dbzfresh(name, size, fs, cmap, tagmask)
+char *name;			/* base name; .dir and .pag must exist */
+long size;			/* table size (0 means default) */
+int fs;				/* field-separator character in base file */
+int cmap;			/* case-map algorithm (0 means default) */
+of_t tagmask;			/* 0 default, 1 no tags */
+{
+	register char *fn;
+	struct dbzconfig c;
+	register of_t m;
+	register FILE *f;
+
+	if (pagf != NULL) {
+		DEBUG(("dbzfresh: database already open\n"));
+		return(-1);
+	}
+	if (size != 0 && size < 2) {
+		DEBUG(("dbzfresh: preposterous size (%ld)\n", size));
+		return(-1);
+	}
+
+	/* get default configuration */
+	if (getconf((FILE *)NULL, (FILE *)NULL, &c) < 0)
+		return(-1);	/* "can't happen" */
+
+	/* and mess with it as specified */
+	if (size != 0)
+		c.tsize = size;
+	c.fieldsep = fs;
+	switch (cmap) {
+	case 0:
+	case '0':
+	case 'B':		/* 2.10 compat */
+		c.casemap = '0';	/* '\0' nicer, but '0' printable! */
+		break;
+	case '=':
+	case 'b':		/* 2.11 compat */
+		c.casemap = '=';
+		break;
+	case 'C':
+		c.casemap = 'C';
+		break;
+	case '?':
+		c.casemap = DEFCASE;
+		break;
+	default:
+		DEBUG(("dbzfresh case map `%c' unknown\n", cmap));
+		return(-1);
+		break;
+	}
+	switch (tagmask) {
+	case 0:			/* default */
+		break;
+	case 1:			/* no tags */
+		c.tagshift = 0;
+		c.tagmask = 0;
+		c.tagenb = 0;
+		break;
+	default:
+		m = tagmask;
+		c.tagshift = 0;
+		while (!(m&01)) {
+			m >>= 1;
+			c.tagshift++;
+		}
+		c.tagmask = m;
+		c.tagenb = (m << 1) & ~m;
+		break;
+	}
+
+	/* write it out */
+	fn = enstring(name, dir);
+	if (fn == NULL)
+		return(-1);
+	f = fopen(fn, "w");
+	free(fn);
+	if (f == NULL) {
+		DEBUG(("dbzfresh: unable to write config\n"));
+		return(-1);
+	}
+	if (putconf(f, &c) < 0) {
+		(void) fclose(f);
+		return(-1);
+	}
+	if (fclose(f) == EOF) {
+		DEBUG(("dbzfresh: fclose failure\n"));
+		return(-1);
+	}
+
+	/* create/truncate .pag */
+	fn = enstring(name, pag);
+	if (fn == NULL)
+		return(-1);
+	f = fopen(fn, "w");
+	free(fn);
+	if (f == NULL) {
+		DEBUG(("dbzfresh: unable to create/truncate .pag file\n"));
+		return(-1);
+	} else
+		(void) fclose(f);
+
+	/* and punt to dbminit for the hard work */
+	return(dbminit(name));
+}
+
+/*
+ - dbzsize - what's a good table size to hold this many entries?
+ */
+long
+dbzsize(contents)
+long contents;			/* 0 means what's the default */
+{
+	register long n;
+
+	if (contents <= 0) {	/* foulup or default inquiry */
+		DEBUG(("dbzsize: preposterous input (%ld)\n", contents));
+		return(DEFSIZE);
+	}
+	n = (contents/2)*3;	/* try to keep table at most 2/3 full */
+	if (!(n&01))		/* make it odd */
+		n++;
+	DEBUG(("dbzsize: tentative size %ld\n", n));
+	while (!isprime(n))	/* and look for a prime */
+		n += 2;
+	DEBUG(("dbzsize: final size %ld\n", n));
+
+	return(n);
+}
+
+/*
+ - isprime - is a number prime?
+ *
+ * This is not a terribly efficient approach.
+ */
+static int			/* predicate */
+isprime(x)
+register long x;
+{
+	static int quick[] = { 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 0 };
+	register int *ip;
+	register long div;
+	register long stop;
+
+	/* hit the first few primes quickly to eliminate easy ones */
+	/* this incidentally prevents ridiculously small tables */
+	for (ip = quick; (div = *ip) != 0; ip++)
+		if (x%div == 0) {
+			DEBUG(("isprime: quick result on %ld\n", (long)x));
+			return(0);
+		}
+
+	/* approximate square root of x */
+	for (stop = x; x/stop < stop; stop >>= 1)
+		continue;
+	stop <<= 1;
+
+	/* try odd numbers up to stop */
+	for (div = *--ip; div < stop; div += 2)
+		if (x%div == 0)
+			return(0);
+
+	return(1);
+}
+
+/*
+ - dbzagain - set up a new database to be a rebuild of an old one
+ */
+int				/* 0 success, -1 failure */
+dbzagain(name, oldname)
+char *name;			/* base name; .dir and .pag must exist */
+char *oldname;			/* base name; all must exist */
+{
+	register char *fn;
+	struct dbzconfig c;
+	register int i;
+	register long top;
+	register FILE *f;
+	register int newtable;
+	register of_t newsize;
+
+	if (pagf != NULL) {
+		DEBUG(("dbzagain: database already open\n"));
+		return(-1);
+	}
+
+	/* pick up the old configuration */
+	fn = enstring(oldname, dir);
+	if (fn == NULL)
+		return(-1);
+	f = fopen(fn, "r");
+	free(fn);
+	if (f == NULL) {
+		DEBUG(("dbzagain: cannot open old .dir file\n"));
+		return(-1);
+	}
+	i = getconf(f, (FILE *)NULL, &c);
+	(void) fclose(f);
+	if (i < 0) {
+		DEBUG(("dbzagain: getconf failed\n"));
+		return(-1);
+	}
+
+	/* tinker with it */
+	top = 0;
+	newtable = 0;
+	for (i = 0; i < NUSEDS; i++) {
+		if (top < c.used[i])
+			top = c.used[i];
+		if (c.used[i] == 0)
+			newtable = 1;	/* hasn't got full usage history yet */
+	}
+	if (top == 0) {
+		DEBUG(("dbzagain: old table has no contents!\n"));
+		newtable = 1;
+	}
+	for (i = NUSEDS-1; i > 0; i--)
+		c.used[i] = c.used[i-1];
+	c.used[0] = 0;
+	newsize = dbzsize(top);
+	if (!newtable || newsize > c.tsize)	/* don't shrink new table */
+		c.tsize = newsize;
+
+	/* write it out */
+	fn = enstring(name, dir);
+	if (fn == NULL)
+		return(-1);
+	f = fopen(fn, "w");
+	free(fn);
+	if (f == NULL) {
+		DEBUG(("dbzagain: unable to write new .dir\n"));
+		return(-1);
+	}
+	i = putconf(f, &c);
+	(void) fclose(f);
+	if (i < 0) {
+		DEBUG(("dbzagain: putconf failed\n"));
+		return(-1);
+	}
+
+	/* create/truncate .pag */
+	fn = enstring(name, pag);
+	if (fn == NULL)
+		return(-1);
+	f = fopen(fn, "w");
+	free(fn);
+	if (f == NULL) {
+		DEBUG(("dbzagain: unable to create/truncate .pag file\n"));
+		return(-1);
+	} else
+		(void) fclose(f);
+
+	/* and let dbminit do the work */
+	return(dbminit(name));
+}
+
+/*
+ - dbminit - open a database, creating it (using defaults) if necessary
+ *
+ * We try to leave errno set plausibly, to the extent that underlying
+ * functions permit this, since many people consult it if dbminit() fails.
+ */
+int 				/* 0 success, -1 failure */
+dbminit(name)
+char *name;
+{
+	register int i;
+	register size_t s;
+	register char *dirfname;
+	register char *pagfname;
+
+	if (pagf != NULL) {
+		DEBUG(("dbminit: dbminit already called once\n"));
+		errno = 0;
+		return(-1);
+	}
+
+	/* open the .dir file */
+	dirfname = enstring(name, dir);
+	if (dirfname == NULL)
+		return(-1);
+	dirf = fopen(dirfname, "r+");
+	if (dirf == NULL) {
+		dirf = fopen(dirfname, "r");
+		dirronly = 1;
+	} else
+		dirronly = 0;
+	free(dirfname);
+	if (dirf == NULL) {
+		DEBUG(("dbminit: can't open .dir file\n"));
+		return(-1);
+	}
+
+	/* open the .pag file */
+	pagfname = enstring(name, pag);
+	if (pagfname == NULL) {
+		(void) fclose(dirf);
+		return(-1);
+	}
+	pagf = fopen(pagfname, "r+b");
+	if (pagf == NULL) {
+		pagf = fopen(pagfname, "rb");
+		if (pagf == NULL) {
+			DEBUG(("dbminit: .pag open failed\n"));
+			(void) fclose(dirf);
+			free(pagfname);
+			return(-1);
+		}
+		pagronly = 1;
+	} else if (dirronly)
+		pagronly = 1;
+	else
+		pagronly = 0;
+#ifdef NOBUFFER
+	/*
+	 * B News does not do adequate locking on its database accesses.
+	 * Why it doesn't get into trouble using dbm is a mystery.  In any
+	 * case, doing unbuffered i/o does not cure the problem, but does
+	 * enormously reduce its incidence.
+	 */
+	(void) setbuf(pagf, (char *)NULL);
+#else
+#ifdef _IOFBF
+	(void) setvbuf(pagf, (char *)pagbuf, _IOFBF, sizeof(pagbuf));
+#endif
+#endif
+	pagpos = -1;
+	/* don't free pagfname, need it below */
+
+	/* open the base file */
+	basef = fopen(name, "r");
+	if (basef == NULL) {
+		DEBUG(("dbminit: basefile open failed\n"));
+		basefname = enstring(name, "");
+		if (basefname == NULL) {
+			(void) fclose(pagf);
+			(void) fclose(dirf);
+			free(pagfname);
+			pagf = NULL;
+			return(-1);
+		}
+	} else
+		basefname = NULL;
+#ifdef _IOFBF
+	if (basef != NULL)
+		(void) setvbuf(basef, basebuf, _IOFBF, sizeof(basebuf));
+#endif
+
+	/* pick up configuration */
+	if (getconf(dirf, pagf, &conf) < 0) {
+		DEBUG(("dbminit: getconf failure\n"));
+		(void) fclose(basef);
+		(void) fclose(pagf);
+		(void) fclose(dirf);
+		free(pagfname);
+		pagf = NULL;
+		errno = EDOM;	/* kind of a kludge, but very portable */
+		return(-1);
+	}
+	tagbits = conf.tagmask << conf.tagshift;
+	taghere = conf.tagenb << conf.tagshift;
+	tagboth = tagbits | taghere;
+	mybytemap(mybmap);
+	bytesame = 1;
+	for (i = 0; i < SOF; i++)
+		if (mybmap[i] != conf.bytemap[i])
+			bytesame = 0;
+
+	/* get first table into core, if it looks desirable and feasible */
+	s = (size_t)conf.tsize * SOF;
+	if (incore && (of_t)(s/SOF) == conf.tsize) {
+		bufpagf = fopen(pagfname, (pagronly) ? "rb" : "r+b");
+		if (bufpagf != NULL)
+			corepag = getcore(bufpagf);
+	} else {
+		bufpagf = NULL;
+		corepag = NULL;
+	}
+	free(pagfname);
+
+	/* misc. setup */
+	crcinit();
+	written = 0;
+	prevp = FRESH;
+	DEBUG(("dbminit: succeeded\n"));
+	return(0);
+}
+
+/*
+ - enstring - concatenate two strings into a malloced area
+ */
+static char *			/* NULL if malloc fails */
+enstring(s1, s2)
+char *s1;
+char *s2;
+{
+	register char *p;
+
+	p = malloc((size_t)strlen(s1) + (size_t)strlen(s2) + 1);
+	if (p != NULL) {
+		(void) strcpy(p, s1);
+		(void) strcat(p, s2);
+	} else {
+		DEBUG(("enstring(%s, %s) out of memory\n", s1, s2));
+	}
+	return(p);
+}
+
+/*
+ - dbmclose - close a database
+ */
+int
+dbmclose()
+{
+	register int ret = 0;
+
+	if (pagf == NULL) {
+		DEBUG(("dbmclose: not opened!\n"));
+		return(-1);
+	}
+
+	if (fclose(pagf) == EOF) {
+		DEBUG(("dbmclose: fclose(pagf) failed\n"));
+		ret = -1;
+	}
+	pagf = basef;		/* ensure valid pointer; dbzsync checks it */
+	if (dbzsync() < 0)
+		ret = -1;
+	if (bufpagf != NULL && fclose(bufpagf) == EOF) {
+		DEBUG(("dbmclose: fclose(bufpagf) failed\n"));
+		ret = -1;
+	}
+	if (corepag != NULL)
+		free((char *)corepag);
+	corepag = NULL;
+	if (fclose(basef) == EOF) {
+		DEBUG(("dbmclose: fclose(basef) failed\n"));
+		ret = -1;
+	}
+	if (basefname != NULL)
+		free(basefname);
+	basef = NULL;
+	pagf = NULL;
+	if (fclose(dirf) == EOF) {
+		DEBUG(("dbmclose: fclose(dirf) failed\n"));
+		ret = -1;
+	}
+
+	DEBUG(("dbmclose: %s\n", (ret == 0) ? "succeeded" : "failed"));
+	return(ret);
+}
+
+/*
+ - dbzsync - push all in-core data out to disk
+ */
+int
+dbzsync()
+{
+	register int ret = 0;
+
+	if (pagf == NULL) {
+		DEBUG(("dbzsync: not opened!\n"));
+		return(-1);
+	}
+	if (!written)
+		return(0);
+
+	if (corepag != NULL) {
+		if (putcore(corepag, bufpagf) < 0) {
+			DEBUG(("dbzsync: putcore failed\n"));
+			ret = -1;
+		}
+	}
+	if (!conf.olddbz)
+		if (putconf(dirf, &conf) < 0)
+			ret = -1;
+
+	DEBUG(("dbzsync: %s\n", (ret == 0) ? "succeeded" : "failed"));
+	return(ret);
+}
+
+/*
+ - dbzcancel - cancel writing of in-core data
+ * Mostly for use from child processes.
+ * Note that we don't need to futz around with stdio buffers, because we
+ * always fflush them immediately anyway and so they never have stale data.
+ */
+int
+dbzcancel()
+{
+	if (pagf == NULL) {
+		DEBUG(("dbzcancel: not opened!\n"));
+		return(-1);
+	}
+
+	written = 0;
+	return(0);
+}
+
+/*
+ - dbzfetch - fetch() with case mapping built in
+ */
+datum
+dbzfetch(key)
+datum key;
+{
+	char buffer[DBZMAXKEY + 1];
+	datum mappedkey;
+	register size_t keysize;
+
+	DEBUG(("dbzfetch: (%s)\n", key.dptr));
+
+	/* Key is supposed to be less than DBZMAXKEY */
+	keysize = key.dsize;
+	if (keysize >= DBZMAXKEY) {
+		keysize = DBZMAXKEY;
+		DEBUG(("keysize is %d - truncated to %d\n", key.dsize, DBZMAXKEY));
+	}
+
+	mappedkey.dptr = mapcase(buffer, key.dptr, keysize);
+	buffer[keysize] = '\0';	/* just a debug aid */
+	mappedkey.dsize = keysize;
+
+	return(fetch(mappedkey));
+}
+
+/*
+ - fetch - get an entry from the database
+ *
+ * Disgusting fine point, in the name of backward compatibility:  if the
+ * last character of "key" is a NUL, that character is (effectively) not
+ * part of the comparison against the stored keys.
+ */
+datum				/* dptr NULL, dsize 0 means failure */
+fetch(key)
+datum key;
+{
+	char buffer[DBZMAXKEY + 1];
+	static of_t key_ptr;		/* return value points here */
+	datum output;
+	register size_t keysize;
+	register size_t cmplen;
+	register char *sepp;
+
+	DEBUG(("fetch: (%s)\n", key.dptr));
+	output.dptr = NULL;
+	output.dsize = 0;
+	prevp = FRESH;
+
+	/* Key is supposed to be less than DBZMAXKEY */
+	keysize = key.dsize;
+	if (keysize >= DBZMAXKEY) {
+		keysize = DBZMAXKEY;
+		DEBUG(("keysize is %d - truncated to %d\n", key.dsize, DBZMAXKEY));
+	}
+
+	if (pagf == NULL) {
+		DEBUG(("fetch: database not open!\n"));
+		return(output);
+	} else if (basef == NULL) {	/* basef didn't exist yet */
+		basef = latebase();
+		if (basef == NULL)
+			return(output);
+	}
+
+	cmplen = keysize;
+	sepp = &conf.fieldsep;
+	if (key.dptr[keysize-1] == '\0') {
+		cmplen--;
+		sepp = &buffer[keysize-1];
+	}
+	start(&srch, &key, FRESH);
+	while ((key_ptr = search(&srch)) != NOTFOUND) {
+		DEBUG(("got 0x%lx\n", key_ptr));
+
+		/* fetch the key */
+		if (fseek(basef, key_ptr, SEEK_SET) != 0) {
+			DEBUG(("fetch: seek failed\n"));
+			return(output);
+		}
+		if (fread(buffer, 1, keysize, basef) != keysize) {
+			DEBUG(("fetch: read failed\n"));
+			return(output);
+		}
+
+		/* try it */
+		buffer[keysize] = '\0';		/* terminated for DEBUG */
+		(void) mapcase(buffer, buffer, keysize);
+		DEBUG(("fetch: buffer (%s) looking for (%s) size = %d\n", 
+						buffer, key.dptr, keysize));
+		if (memcmp(key.dptr, buffer, cmplen) == 0 &&
+				(*sepp == conf.fieldsep || *sepp == '\0')) {
+			/* we found it */
+			output.dptr = (char *)&key_ptr;
+			output.dsize = SOF;
+			DEBUG(("fetch: successful\n"));
+			return(output);
+		}
+	}
+
+	/* we didn't find it */
+	DEBUG(("fetch: failed\n"));
+	prevp = &srch;			/* remember where we stopped */
+	return(output);
+}
+
+/*
+ - latebase - try to open a base file that wasn't there at the start
+ */
+static FILE *
+latebase()
+{
+	register FILE *it;
+
+	if (basefname == NULL) {
+		DEBUG(("latebase: name foulup\n"));
+		return(NULL);
+	}
+	it = fopen(basefname, "r");
+	if (it == NULL) {
+		DEBUG(("latebase: still can't open base\n"));
+	} else {
+		DEBUG(("latebase: late open succeeded\n"));
+		free(basefname);
+		basefname = NULL;
+#ifdef _IOFBF
+		(void) setvbuf(it, basebuf, _IOFBF, sizeof(basebuf));
+#endif
+	}
+	return(it);
+}
+
+/*
+ - dbzstore - store() with case mapping built in
+ */
+int
+dbzstore(key, data)
+datum key;
+datum data;
+{
+	char buffer[DBZMAXKEY + 1];
+	datum mappedkey;
+	register size_t keysize;
+
+	DEBUG(("dbzstore: (%s)\n", key.dptr));
+
+	/* Key is supposed to be less than DBZMAXKEY */
+	keysize = key.dsize;
+	if (keysize >= DBZMAXKEY) {
+		DEBUG(("dbzstore: key size too big (%d)\n", key.dsize));
+		return(-1);
+	}
+
+	mappedkey.dptr = mapcase(buffer, key.dptr, keysize);
+	buffer[keysize] = '\0';	/* just a debug aid */
+	mappedkey.dsize = keysize;
+
+	return(store(mappedkey, data));
+}
+
+/*
+ - store - add an entry to the database
+ */
+int				/* 0 success, -1 failure */
+store(key, data)
+datum key;
+datum data;
+{
+	of_t value;
+
+	if (pagf == NULL) {
+		DEBUG(("store: database not open!\n"));
+		return(-1);
+	} else if (basef == NULL) {	/* basef didn't exist yet */
+		basef = latebase();
+		if (basef == NULL)
+			return(-1);
+	}
+	if (pagronly) {
+		DEBUG(("store: database open read-only\n"));
+		return(-1);
+	}
+	if (data.dsize != SOF) {
+		DEBUG(("store: value size wrong (%d)\n", data.dsize));
+		return(-1);
+	}
+	if (key.dsize >= DBZMAXKEY) {
+		DEBUG(("store: key size too big (%d)\n", key.dsize));
+		return(-1);
+	}
+
+	/* copy the value in to ensure alignment */
+	(void) memcpy((char *)&value, data.dptr, SOF);
+	DEBUG(("store: (%s, %ld)\n", key.dptr, (long)value));
+	if (!okayvalue(value)) {
+		DEBUG(("store: reserved bit or overflow in 0x%lx\n", value));
+		return(-1);
+	}
+
+	/* find the place, exploiting previous search if possible */
+	start(&srch, &key, prevp);
+	while (search(&srch) != NOTFOUND)
+		continue;
+
+	prevp = FRESH;
+	conf.used[0]++;
+	DEBUG(("store: used count %ld\n", conf.used[0]));
+	written = 1;
+	return(set(&srch, value));
+}
+
+/*
+ - dbzincore - control attempts to keep .pag file in core
+ */
+int				/* old setting */
+dbzincore(value)
+int value;
+{
+	register int old = incore;
+
+	incore = value;
+	return(old);
+}
+
+/*
+ - getconf - get configuration from .dir file
+ */
+static int			/* 0 success, -1 failure */
+getconf(df, pf, cp)
+register FILE *df;		/* NULL means just give me the default */
+register FILE *pf;		/* NULL means don't care about .pag */
+register struct dbzconfig *cp;
+{
+	register int c;
+	register int i;
+	int err = 0;
+
+	c = (df != NULL) ? getc(df) : EOF;
+	if (c == EOF) {		/* empty file, no configuration known */
+		cp->olddbz = 0;
+		if (df != NULL && pf != NULL && getc(pf) != EOF)
+			cp->olddbz = 1;
+		cp->tsize = DEFSIZE;
+		cp->fieldsep = '\t';
+		for (i = 0; i < NUSEDS; i++)
+			cp->used[i] = 0;
+		cp->valuesize = SOF;
+		mybytemap(cp->bytemap);
+		cp->casemap = DEFCASE;
+		cp->tagenb = TAGENB;
+		cp->tagmask = TAGMASK;
+		cp->tagshift = TAGSHIFT;
+		DEBUG(("getconf: defaults (%ld, %c, (0x%lx/0x%lx<<%d))\n",
+			cp->tsize, cp->casemap, cp->tagenb, 
+			cp->tagmask, cp->tagshift));
+		return(0);
+	}
+	(void) ungetc(c, df);
+
+	/* first line, the vital stuff */
+	if (getc(df) != 'd' || getc(df) != 'b' || getc(df) != 'z')
+		err = -1;
+	if (getno(df, &err) != dbzversion)
+		err = -1;
+	cp->tsize = getno(df, &err);
+	cp->fieldsep = getno(df, &err);
+	while ((c = getc(df)) == ' ')
+		continue;
+	cp->casemap = c;
+	cp->tagenb = getno(df, &err);
+	cp->tagmask = getno(df, &err);
+	cp->tagshift = getno(df, &err);
+	cp->valuesize = getno(df, &err);
+	if (cp->valuesize != SOF) {
+		DEBUG(("getconf: wrong of_t size (%d)\n", cp->valuesize));
+		err = -1;
+		cp->valuesize = SOF;	/* to protect the loops below */
+	}
+	for (i = 0; i < cp->valuesize; i++)
+		cp->bytemap[i] = getno(df, &err);
+	if (getc(df) != '\n')
+		err = -1;
+	DEBUG(("size %ld, sep %d, cmap %c, tags 0x%lx/0x%lx<<%d, ", cp->tsize,
+			cp->fieldsep, cp->casemap, cp->tagenb, cp->tagmask,
+			cp->tagshift));
+	DEBUG(("bytemap (%d)", cp->valuesize));
+	for (i = 0; i < cp->valuesize; i++) {
+		DEBUG((" %d", cp->bytemap[i]));
+	}
+	DEBUG(("\n"));
+
+	/* second line, the usages */
+	for (i = 0; i < NUSEDS; i++)
+		cp->used[i] = getno(df, &err);
+	if (getc(df) != '\n')
+		err = -1;
+	DEBUG(("used %ld %ld %ld...\n", cp->used[0], cp->used[1], cp->used[2]));
+
+	if (err < 0) {
+		DEBUG(("getconf error\n"));
+		return(-1);
+	}
+	return(0);
+}
+
+/*
+ - getno - get a long
+ */
+static long
+getno(f, ep)
+FILE *f;
+int *ep;
+{
+	register char *p;
+#	define	MAXN	50
+	char getbuf[MAXN];
+	register int c;
+
+	while ((c = getc(f)) == ' ')
+		continue;
+	if (c == EOF || c == '\n') {
+		DEBUG(("getno: missing number\n"));
+		*ep = -1;
+		return(0);
+	}
+	p = getbuf;
+	*p++ = c;
+	while ((c = getc(f)) != EOF && c != '\n' && c != ' ')
+		if (p < &getbuf[MAXN-1])
+			*p++ = c;
+	if (c == EOF) {
+		DEBUG(("getno: EOF\n"));
+		*ep = -1;
+	} else
+		(void) ungetc(c, f);
+	*p = '\0';
+
+	if (strspn(getbuf, "-1234567890") != strlen(getbuf)) {
+		DEBUG(("getno: `%s' non-numeric\n", getbuf));
+		*ep = -1;
+	}
+	return(atol(getbuf));
+}
+
+/*
+ - putconf - write configuration to .dir file
+ */
+static int			/* 0 success, -1 failure */
+putconf(f, cp)
+register FILE *f;
+register struct dbzconfig *cp;
+{
+	register int i;
+	register int ret = 0;
+
+	if (fseek(f, (of_t)0, SEEK_SET) != 0) {
+		DEBUG(("fseek failure in putconf\n"));
+		ret = -1;
+	}
+	fprintf(f, "dbz %d %ld %d %c %ld %ld %d %d", dbzversion, cp->tsize,
+				cp->fieldsep, cp->casemap, cp->tagenb,
+				cp->tagmask, cp->tagshift, cp->valuesize);
+	for (i = 0; i < cp->valuesize; i++)
+		fprintf(f, " %d", cp->bytemap[i]);
+	fprintf(f, "\n");
+	for (i = 0; i < NUSEDS; i++)
+		fprintf(f, "%ld%c", cp->used[i], (i < NUSEDS-1) ? ' ' : '\n');
+
+	(void) fflush(f);
+	if (ferror(f))
+		ret = -1;
+
+	DEBUG(("putconf status %d\n", ret));
+	return(ret);
+}
+
+/*
+ - getcore - try to set up an in-core copy of .pag file
+ */
+static of_t *			/* pointer to copy, or NULL */
+getcore(f)
+FILE *f;
+{
+	register of_t *p;
+	register size_t i;
+	register size_t nread;
+	register char *it;
+
+	it = malloc((size_t)conf.tsize * SOF);
+	if (it == NULL) {
+		DEBUG(("getcore: malloc failed\n"));
+		return(NULL);
+	}
+
+	nread = fread(it, SOF, (size_t)conf.tsize, f);
+	if (ferror(f)) {
+		DEBUG(("getcore: read failed\n"));
+		free(it);
+		return(NULL);
+	}
+
+	p = (of_t *)it + nread;
+	i = (size_t)conf.tsize - nread;
+	while (i-- > 0)
+		*p++ = VACANT;
+	return((of_t *)it);
+}
+
+/*
+ - putcore - try to rewrite an in-core table
+ */
+static int			/* 0 okay, -1 fail */
+putcore(tab, f)
+of_t *tab;
+FILE *f;
+{
+	if (fseek(f, (of_t)0, SEEK_SET) != 0) {
+		DEBUG(("fseek failure in putcore\n"));
+		return(-1);
+	}
+	(void) fwrite((char *)tab, SOF, (size_t)conf.tsize, f);
+	(void) fflush(f);
+	return((ferror(f)) ? -1 : 0);
+}
+
+/*
+ - start - set up to start or restart a search
+ */
+static void
+start(sp, kp, osp)
+register struct searcher *sp;
+register datum *kp;
+register struct searcher *osp;		/* may be FRESH, i.e. NULL */
+{
+	register long h;
+
+	h = hash(kp->dptr, kp->dsize);
+	if (osp != FRESH && osp->hash == h) {
+		if (sp != osp)
+			*sp = *osp;
+		DEBUG(("search restarted\n"));
+	} else {
+		sp->hash = h;
+		sp->tag = MKTAG(h / conf.tsize);
+		DEBUG(("tag 0x%lx\n", sp->tag));
+		sp->place = h % conf.tsize;
+		sp->tabno = 0;
+		sp->run = (conf.olddbz) ? conf.tsize : MAXRUN;
+		sp->aborted = 0;
+	}
+	sp->seen = 0;
+}
+
+/*
+ - search - conduct part of a search
+ */
+static of_t			/* NOTFOUND if we hit VACANT or error */
+search(sp)
+register struct searcher *sp;
+{
+	register of_t dest;
+	register of_t value;
+	of_t val;		/* buffer for value (can't fread register) */
+	register of_t place;
+
+	if (sp->aborted)
+		return(NOTFOUND);
+
+	for (;;) {
+		/* determine location to be examined */
+		place = sp->place;
+		if (sp->seen) {
+			/* go to next location */
+			if (--sp->run <= 0) {
+				sp->tabno++;
+				sp->run = MAXRUN;
+			}
+			place = (place+1)%conf.tsize + sp->tabno*conf.tsize;
+			sp->place = place;
+		} else
+			sp->seen = 1;	/* now looking at current location */
+		DEBUG(("search @ %ld\n", place));
+
+		/* get the tagged value */
+		if (corepag != NULL && place < conf.tsize) {
+			DEBUG(("search: in core\n"));
+			value = MAPIN(corepag[place]);
+		} else {
+			/* seek, if necessary */
+			dest = place * SOF;
+			if (pagpos != dest) {
+				if (fseek(pagf, dest, SEEK_SET) != 0) {
+					DEBUG(("search: seek failed\n"));
+					pagpos = -1;
+					sp->aborted = 1;
+					return(NOTFOUND);
+				}
+				pagpos = dest;
+			}
+
+			/* read it */
+			if (fread((char *)&val, sizeof(val), 1, pagf) == 1)
+				value = MAPIN(val);
+			else if (ferror(pagf)) {
+				DEBUG(("search: read failed\n"));
+				pagpos = -1;
+				sp->aborted = 1;
+				return(NOTFOUND);
+			} else
+				value = VACANT;
+
+			/* and finish up */
+			pagpos += sizeof(val);
+		}
+
+		/* vacant slot is always cause to return */
+		if (value == VACANT) {
+			DEBUG(("search: empty slot\n"));
+			return(NOTFOUND);
+		};
+
+		/* check the tag */
+		value = UNBIAS(value);
+		DEBUG(("got 0x%lx\n", value));
+		if (!HASTAG(value)) {
+			DEBUG(("tagless\n"));
+			return(value);
+		} else if (TAG(value) == sp->tag) {
+			DEBUG(("match\n"));
+			return(NOTAG(value));
+		} else {
+			DEBUG(("mismatch 0x%lx\n", TAG(value)));
+		}
+	}
+	/* NOTREACHED */
+}
+
+/*
+ - okayvalue - check that a value can be stored
+ */
+static int			/* predicate */
+okayvalue(value)
+of_t value;
+{
+	if (HASTAG(value))
+		return(0);
+#ifdef OVERFLOW
+	if (value == LONG_MAX)	/* BIAS() and UNBIAS() will overflow */
+		return(0);
+#endif
+	return(1);
+}
+
+/*
+ - set - store a value into a location previously found by search
+ */
+static int			/* 0 success, -1 failure */
+set(sp, value)
+register struct searcher *sp;
+of_t value;
+{
+	register of_t place = sp->place;
+	register of_t v = value;
+
+	if (sp->aborted)
+		return(-1);
+
+	if (CANTAG(v) && !conf.olddbz) {
+		v |= sp->tag | taghere;
+		if (v != UNBIAS(VACANT))	/* BIAS(v) won't look VACANT */
+#ifdef OVERFLOW
+			if (v != LONG_MAX)	/* and it won't overflow */
+#endif
+			value = v;
+	}
+	DEBUG(("tagged value is 0x%lx\n", value));
+	value = BIAS(value);
+	value = MAPOUT(value);
+
+	/* If we have the index file in memory, use it */
+	if (corepag != NULL && place < conf.tsize) {
+		corepag[place] = value;
+		DEBUG(("set: incore\n"));
+		return(0);
+	}
+
+	/* seek to spot */
+	pagpos = -1;		/* invalidate position memory */
+	if (fseek(pagf, place * SOF, SEEK_SET) != 0) {
+		DEBUG(("set: seek failed\n"));
+		sp->aborted = 1;
+		return(-1);
+	}
+
+	/* write in data */
+	if (fwrite((char *)&value, SOF, 1, pagf) != 1) {
+		DEBUG(("set: write failed\n"));
+		sp->aborted = 1;
+		return(-1);
+	}
+	/* fflush improves robustness, and buffer re-use is rare anyway */
+	if (fflush(pagf) == EOF) {
+		DEBUG(("set: fflush failed\n"));
+		sp->aborted = 1;
+		return(-1);
+	}
+
+	DEBUG(("set: succeeded\n"));
+	return(0);
+}
+
+/*
+ - mybytemap - determine this machine's byte map
+ *
+ * A byte map is an array of ints, sizeof(of_t) of them.  The 0th int
+ * is the byte number of the high-order byte in my of_t, and so forth.
+ */
+static void
+mybytemap(map)
+int map[];			/* -> int[SOF] */
+{
+	union {
+		of_t o;
+		char c[SOF];
+	} u;
+	register int *mp = &map[SOF];
+	register int ntodo;
+	register int i;
+
+	u.o = 1;
+	for (ntodo = (int)SOF; ntodo > 0; ntodo--) {
+		for (i = 0; i < SOF; i++)
+			if (u.c[i] != 0)
+				break;
+		if (i == SOF) {
+			/* trouble -- set it to *something* consistent */
+			DEBUG(("mybytemap: nonexistent byte %d!!!\n", ntodo));
+			for (i = 0; i < SOF; i++)
+				map[i] = i;
+			return;
+		}
+		DEBUG(("mybytemap: byte %d\n", i));
+		*--mp = i;
+		while (u.c[i] != 0)
+			u.o <<= 1;
+	}
+}
+
+/*
+ - bytemap - transform an of_t from byte ordering map1 to map2
+ */
+static of_t			/* transformed result */
+bytemap(ino, map1, map2)
+of_t ino;
+int *map1;
+int *map2;
+{
+	union oc {
+		of_t o;
+		char c[SOF];
+	};
+	union oc in;
+	union oc out;
+	register int i;
+
+	in.o = ino;
+	for (i = 0; i < SOF; i++)
+		out.c[map2[i]] = in.c[map1[i]];
+	return(out.o);
+}
+
+/*
+ * This is a simplified version of the pathalias hashing function.
+ * Thanks to Steve Belovin and Peter Honeyman
+ *
+ * hash a string into a long int.  31 bit crc (from andrew appel).
+ * the crc table is computed at run time by crcinit() -- we could
+ * precompute, but it takes 1 clock tick on a 750.
+ *
+ * This fast table calculation works only if POLY is a prime polynomial
+ * in the field of integers modulo 2.  Since the coefficients of a
+ * 32-bit polynomial won't fit in a 32-bit word, the high-order bit is
+ * implicit.  IT MUST ALSO BE THE CASE that the coefficients of orders
+ * 31 down to 25 are zero.  Happily, we have candidates, from
+ * E. J.  Watson, "Primitive Polynomials (Mod 2)", Math. Comp. 16 (1962):
+ *	x^32 + x^7 + x^5 + x^3 + x^2 + x^1 + x^0
+ *	x^31 + x^3 + x^0
+ *
+ * We reverse the bits to get:
+ *	111101010000000000000000000000001 but drop the last 1
+ *         f   5   0   0   0   0   0   0
+ *	010010000000000000000000000000001 ditto, for 31-bit crc
+ *	   4   8   0   0   0   0   0   0
+ */
+
+#define POLY 0x48000000L	/* 31-bit polynomial (avoids sign problems) */
+
+static long CrcTable[128];
+
+/*
+ - crcinit - initialize tables for hash function
+ */
+static void
+crcinit()
+{
+	register int i, j;
+	register long sum;
+
+	for (i = 0; i < 128; ++i) {
+		sum = 0L;
+		for (j = 7 - 1; j >= 0; --j)
+			if (i & (1 << j))
+				sum ^= POLY >> j;
+		CrcTable[i] = sum;
+	}
+	DEBUG(("crcinit: done\n"));
+}
+
+/*
+ - hash - Honeyman's nice hashing function
+ */
+static long
+hash(name, size)
+register char *name;
+register int size;
+{
+	register long sum = 0L;
+
+	while (size--) {
+		sum = (sum >> 7) ^ CrcTable[(sum ^ (*name++)) & 0x7f];
+	}
+	DEBUG(("hash: returns (%ld)\n", sum));
+	return(sum);
+}
+
+/*
+ * case-mapping stuff
+ *
+ * Borrowed from C News, by permission of the authors.  Somewhat modified.
+ *
+ * We exploit the fact that we are dealing only with headers here, and
+ * headers are limited to the ASCII characters by RFC822.  It is barely
+ * possible that we might be dealing with a translation into another
+ * character set, but in particular it's very unlikely for a header
+ * character to be outside -128..255.
+ *
+ * Life would be a whole lot simpler if tolower() could safely and portably
+ * be applied to any char.
+ */
+
+#define	OFFSET	128		/* avoid trouble with negative chars */
+
+/* must call casencmp before invoking TOLOW... */
+#define	TOLOW(c)	(cmap[(c)+OFFSET])
+
+/* ...but the use of it in CISTREQN is safe without the preliminary call (!) */
+/* CISTREQN is an optimised case-insensitive strncmp(a,b,n)==0; n > 0 */
+#define CISTREQN(a, b, n) \
+	(TOLOW((a)[0]) == TOLOW((b)[0]) && casencmp(a, b, n) == 0)
+
+#define	MAPSIZE	(256+OFFSET)
+static char cmap[MAPSIZE];	/* relies on init to '\0' */
+static int mprimed = 0;		/* has cmap been set up? */
+
+/*
+ - mapprime - set up case-mapping stuff
+ */
+static void
+mapprime()
+{
+	register char *lp;
+	register char *up;
+	register int c;
+	register int i;
+	static char lower[] = "abcdefghijklmnopqrstuvwxyz";
+	static char upper[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+	for (lp = lower, up = upper; *lp != '\0'; lp++, up++) {
+		c = *lp;
+		cmap[c+OFFSET] = c;
+		cmap[*up+OFFSET] = c;
+	}
+	for (i = 0; i < MAPSIZE; i++)
+		if (cmap[i] == '\0')
+			cmap[i] = (char)(i-OFFSET);
+	mprimed = 1;
+}
+
+/*
+ - casencmp - case-independent strncmp
+ */
+static int			/* < == > 0 */
+casencmp(s1, s2, len)
+char *s1;
+char *s2;
+int len;
+{
+	register char *p1;
+	register char *p2;
+	register int n;
+
+	if (!mprimed)
+		mapprime();
+
+	p1 = s1;
+	p2 = s2;
+	n = len;
+	while (--n >= 0 && *p1 != '\0' && TOLOW(*p1) == TOLOW(*p2)) {
+		p1++;
+		p2++;
+	}
+	if (n < 0)
+		return(0);
+
+	/*
+	 * The following case analysis is necessary so that characters
+	 * which look negative collate low against normal characters but
+	 * high against the end-of-string NUL.
+	 */
+	if (*p1 == '\0' && *p2 == '\0')
+		return(0);
+	else if (*p1 == '\0')
+		return(-1);
+	else if (*p2 == '\0')
+		return(1);
+	else
+		return(TOLOW(*p1) - TOLOW(*p2));
+}
+
+/*
+ - mapcase - do case-mapped copy
+ */
+static char *			/* returns src or dst */
+mapcase(dst, src, siz)
+char *dst;			/* destination, used only if mapping needed */
+char *src;			/* source; src == dst is legal */
+size_t siz;
+{
+	register char *s;
+	register char *d;
+	register char *c;	/* case break */
+	register char *e;	/* end of source */
+
+
+	c = cipoint(src, siz);
+	if (c == NULL)
+		return(src);
+
+	if (!mprimed)
+		mapprime();
+	s = src;
+	e = s + siz;
+	d = dst;
+
+	while (s < c)
+		*d++ = *s++;
+	while (s < e)
+		*d++ = TOLOW(*s++);
+
+	return(dst);
+}
+
+/*
+ - cipoint - where in this message-ID does it become case-insensitive?
+ *
+ * The RFC822 code is not quite complete.  Absolute, total, full RFC822
+ * compliance requires a horrible parsing job, because of the arcane
+ * quoting conventions -- abc"def"ghi is not equivalent to abc"DEF"ghi,
+ * for example.  There are three or four things that might occur in the
+ * domain part of a message-id that are case-sensitive.  They don't seem
+ * to ever occur in real news, thank Cthulhu.  (What?  You were expecting
+ * a merciful and forgiving deity to be invoked in connection with RFC822?
+ * Forget it; none of them would come near it.)
+ */
+static char *			/* pointer into s, or NULL for "nowhere" */
+cipoint(s, siz)
+char *s;
+size_t siz;
+{
+	register char *p;
+	static char post[] = "postmaster";
+	static int plen = sizeof(post)-1;
+
+	switch (conf.casemap) {
+	case '0':		/* unmapped, sensible */
+		return(NULL);
+		break;
+	case 'C':		/* C News, RFC 822 conformant (approx.) */
+		p = memchr(s, '@', siz);
+		if (p == NULL)			/* no local/domain split */
+			return(NULL);		/* assume all local */
+		else if	(p - (s+1) == plen && CISTREQN(s+1, post, plen)) {
+			/* crazy -- "postmaster" is case-insensitive */
+			return(s);
+		} else
+			return(p);
+		break;
+	case '=':		/* 2.11, neither sensible nor conformant */
+		return(s);	/* all case-insensitive */
+		break;
+	}
+
+	DEBUG(("cipoint: unknown case mapping `%c'\n", conf.casemap));
+	return(NULL);		/* just leave it alone */
+}
+
+/*
+ - dbzdebug - control dbz debugging at run time
+ */
+int				/* old value */
+dbzdebug(value)
+int value;
+{
+#ifdef DBZDEBUG
+	register int old = debug;
+
+	debug = value;
+	return(old);
+#else
+	return(-1);
+#endif
+}